Epigenetic responses to stress: triple defense?

Abstract

Stressful conditions for plants can originate from numerous physical, chemical and biological factors, and plants have developed a plethora of survival strategies including developmental and morphological adaptations, specific signaling and defense pathways as well as innate and acquired immunity. While it has become clear in recent years that many stress responses involve epigenetic components, we are far from understanding the mechanisms and molecular interactions. Extending our knowledge is fundamental, not least for plant breeding and conservation biology. This review will highlight recent insights into epigenetic stress responses at the level of signaling, chromatin modification, and potentially heritable consequences.

Figure 1

Abiotic and biotic stress conditions (a) can change gene expression with and without involving plant stress hormones (b). Transcription changes, or stress factors directly, can affect chromatin via DNA methylation, histone tail modifications, histone variant replacements, or nucleosome loss and chromatin de-condensation (c, d). These changes are largely reversible but can modify metabolic or morphologic plant features under stress conditions. Usually, the new phenotypes are not transmitted to progeny. However, chromatin-associated changes have the potential to be heritable and might result in uniform maintenance of new features or new combination and epigenetic diversity (e).